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Abstract

In aqueous solutions exposed to sunlight, resorcinol, a m-dihydroxyphenol, does not undergo autoxidation as compared to catechol, an o-dihydroxyphenol. However, water taken from a lake (Schöhsee, Plön) caused a disappearance of resorcinol and enhanced catechol conversion. A screening involving species of various algae groups showed that resorcinol was being converted specifically by members of the Cryptophyceae family. The algae could be separated by ultrafiltration from the culture medium with full viability; the activity was found in the medium and could be characterized by protein precipitation and denaturation as a Cryptomonad exoenzyme with a M.W. congruent to 10⁵. The conversion rates of resorcinol increased exponentially during successive additions of substrate, pointing to a reaction on which the product functions as an increasing matrix for the addition of next substrate molecules. After seven resorcinol pulses of about 30 nmol/ml resorcinol to the same enzyme source, irregularly-shaped, water-insoluble crystals appeared as reaction products. The algae themselves, however, were severely affected after the third resorcinol application and did not survive subsequent addition. In the freshwater research, this result represents the complete sequence of an allelopathic interaction between resorcinol exuding aquatic macrophytes and surrounding microphytes; it may also contribute to the solution of open questions about the origin and turnover of phenolic DOM in aqueous systems. In environmental terms, it questions the role of industrial wastewater inputs, and on one hand the toxicity of resorcinol and on the other hand, the detoxification capability of natural waters. Lastly, it should be considered that this kind of enzymatic monophenol condensation could also participate in the synthesis of various polyphenolic compounds of higher terrestrial plants.